This invention generally relates to ultrasound probes having an array of piezoelectric transducer elements. In particular, the invention relates to systems for electrically connecting the transducer array of an ultrasound probe to a coaxial cable.
A typical ultrasound probe consists of three basic parts: (1) a transducer package; (2) a multi-wire coaxial cable connecting the transducer to the rest of the ultrasound system; and (3) other miscellaneous mechanical hardware such as the probe housing, thermal/acoustic potting material and electrical shielding. The transducer package (sometimes referred to as a xe2x80x9cpalletxe2x80x9d) is typically produced by stacking layers in sequence. This involves a high density of interconnections and, as the density of interconnections to ultrasonic transducer arrays increases, so does the complexity of these connections. The standard methods of interconnect on multi-row transducer arrays, such as flex boards extending in a plane parallel to the surface of the transducer, are geometrically constrained and also tend to interfere with the acoustics and dicing of the transducer.
The present invention concerns an acoustic backing and interconnect module and a method of using the volume of the acoustic backing layer to make the interconnections to an ultrasonic array reliably and efficiently.
A combined acoustic backing and interconnect module for connecting an array of ultrasonic transducer elements to a multiplicity of conductors of a cable utilizes the volume of the backing layer to extend a high density of interconnections perpendicular to the surface of the transducer array. The invention further comprises a method for manufacturing such an acoustic backing and interconnect module by injection molding.
The invention is particularly advantageous when used to construct multi-row transducer arrays, such as 1.25D (elevation aperture is variable, but focusing remains static), 1.5D (elevation aperture, shading, and focusing are dynamically variable, but symmetric about the horizontal centerline of the array) and 2D (elevation geometry and performance are comparable to azimuth, with full electronic apodization, focusing and steering arrays). However, the invention can also be used to manufacture single-row transducer arrays.
In accordance with the invention, an ultrasonic transducer array made up of piezoelectric ceramic elements is provided with a high-density interconnection to the piezoelectric ceramic elements which extends through the acoustic backing layer. In accordance with a preferred method of manufacture, a mold for an acoustic backing and interconnect module is assembled by alternately stacking spacer plates and flexible circuit boards. Each spacer plate has a spacer channel defined in part by a first planar wall. The spacer channels are aligned when the mold is assembled so that the first planar walls are coplanar. Each flexible circuit board has an opening which aligns with one end of the spacer channels. The acoustic backfill material is injected into the mold, filling each channel. After the backfill material has cured to form the backing layer, the flexible, circuit boards are held in spaced parallel relationship. The excess flexible circuit material on the side of the backing layer formed by the coplanar first planar walls is then cut away to expose the ends of the conductors on the flexible circuit boards. When the backing layer is bonded to the piezoelectric ceramic layer, the exposed ends of the conductors are aligned with, and brought into electrical contact with, respective signal electrodes of the transducer array, thereby making the electrical connections between the array elements and the conductive traces on the flexible circuit boards en masse.
Optionally, in accordance with another feature of the invention, contact bumps or pads made of electrically conductive material (e.g., gold) can be plated over the exposed ends of the flexible circuit board conductors to ensure good electrical contact with the signal electrodes.